1. Field of the Invention
The present invention relates to an image forming optical system and an electronic image pickup apparatus equipped with the same.
2. Description of the Related Art
In recent years, digital cameras that pick up an image of an object using a solid state image pickup element such as a CCD or CMOS have replaced film cameras and become the mainstream. Furthermore, various categories of digital cameras ranging from popular-priced compact type cameras to advanced type cameras for professionals have been developed. The present invention is directed mainly to popular-priced compact type cameras.
Users of such popular-priced digital cameras generally wish to enjoy easy and simple shooting in various shooting situations anywhere at any time. For this reason, such users favor small size digital cameras, in particular cameras that are small in thickness and can be conveniently carried in a pocket of clothes or a bag.
Moreover, a further reduction in the size of the taking lens system of such cameras is demanded. In addition, zoom lenses that have a high zoom ratio and a wide angle of view at the wide angle end to allow shooting in various scenes are desired.
Japanese Patent Application Laid-Open Nos. 2008-102165 and 04-104114 disclose zoom lenses that can be designed to have a relatively high zoom ratio. The zoom lenses disclosed in these patent documents have, in order from the object side, a first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, and a fourth lens group having a positive refracting power, wherein zooming is performed by changing the distances between the lens groups.